Tactile drawings, also called raised-line drawings or RLDs, are produced and used primarily by the blind and sight-impaired because they allow tactile sensing in a free-hand drawing. With reference to FIG. 1, tactile drawings are formed in one example by a stylus 10 that is moved and controlled by a user relative to a surface 22 of a locally deformable medium 20, referred to hereinafter as a “tactile drawing medium.” Tactile drawing medium 20 is configured to permanently or semi-permanently display one or more tactile drawing features 30 on surface 22 when localized pressure is applied to the surface with stylus 10. In particular, as a user moves stylus 10 over surface 22 of tactile drawing medium 20 with downward pressure, tactile feature 30 is formed thereon, with the tactile feature instantly revealing the stylus path. The resulting drawing is referred to herein as a tactile drawing 32.
A typical tactile drawing medium 20 comprises a thin plastic sheet, which can be a thermoplastic material (also called thermosoftening plastic), among others. Tactile drawing medium 20 is placed and secured (e.g., via a clip 40, as shown) on top of a pad of flexible or indentable material 24, such as rubber. Stylus 10 can be a typical ballpoint pen (or other rolling contact device), or can simply be a rod with a rounded or otherwise effectively shape tip 12. The force of stylus tip 12 on the flexible material 24 through tactile drawing medium 20 locally plastically deforms the tactile drawing medium to create a tactile feature 30. In an example, the tactile drawing medium responds along the stretched line produced by the stylus by rising instantaneously to become a palpable raised feature. This system has the benefit of letting a user feel what they are drawing while they draw it, and provides a permanent hardcopy of their tactile drawing that others can tactilely sense.
One limitation of tactile drawing medium 20 is that tactile features 30 cannot be removed or erased in a practical manner. Thus, the user does not have the benefit of being able to readily refine tactile drawing 32 by erasing some or all of a given tactile feature 30. Since making such changes is an essential part of the creative process of making a tactile drawing, the inability to erase some or all of a tactile drawing is a significant limitation on the state of the art.